The present invention relates to a structure and technique for ensuring air tightness and waterproof performance of a cord insertion hole formed on a back cover for light source bulb replacement. The structure is installed at the rear apex of a lamp body, which is a basic construction member of a lamp for a vehicle such as an automobile and motorcycle.
More particularly, the present invention relates to an improvement of a lamp body back cover structure. The goal is to ensure air tightness and waterproof performance of the cord insertion hole by forming a resin mold region around the cord insertion hole formed in the back cover, and filling and curing a soft synthetic resin in the resin mold region.
In general, a back cover for light source bulb replacement is engagingly fixed to a light source bulb insertion opening formed at the rear apex of a generally cup-shaped lamp body that forms a housing of a vehicle lamp such as a headlamp for an automobile and motorcycle.
Conventionally, one or a plurality of power supply cords for supplying current from a power source to a light source bulb disposed inside a housing are inserted and fixed to the back cover for a lamp body. Further, a variety of constructions are proposed for ensuring air tightness and waterproof performance of the clearance formed at the power supply cord insertion portion.
Such constructions typically include,
(1) a first configuration, as shown in FIG. 5(A), wherein all power supply cords 21a, 21b for supplying current to a light source bulb, not shown, are inserted and fixed to a rubber bushing 22. The rubber bushing 22 is fitted into a preformed hole 23 formed in a back cover 20a that is engagingly fixed to a lamp body 21; and
(2) a second configuration, which is an improved configuration, as shown in FIG. 5(B), wherein two cord insertion holes 25a, 25b accommodate respective power supply cords 21a, 21b. The cord insertion holes are provided in a back cover 20b (partially shown) at intervals, and cylindrical projections 26a, 26b are provided so as to surround the respective insertion holes 25a, 25b. Small rubber bushings 24a, 24b, with power supply cords 21a, 21b inserted and fixed therein in advance, are fitted into the respective inner region of the protrusions 26a, 26b, and adhesives 27a, 27b are poured from above the small bushings 24a, 24b so as to provide a seal.
In the first construction of FIG. 5(A) mentioned above, the engagement areas between the bushing 22 and the cord insertion hole portion, and between the bushing 22 and the back cover hole 23 tended to be large due to the relatively large bushing 22 used therein. Also, sufficient air tightness and waterproof performance could not be obtained due to a difference in material of the rubber bushing 22 and the synthetic resin back cover 20a. Other technical problems also arose, such as that fitting of the bushing required some effort.
In the second configuration of FIG. 5(B), the assembly work (installing the power supply cord) required steps for inserting and fixing a power supply cord 21 to a bushing 24, a primer processing step for the lamp body, a step for inserting the bushing 24, and a step for filling in an adhesive 27. This resulted in a large number of working man hours. Other technical problems also arose, such as that the holding strength of the power supply cord 21 is weak due to the fact that the adhesive 27 is filled from above the bushing 24.
The present invention has been made in order to solve the drawbacks of the prior art. Particularly, the present invention provides a back cover for a lamp body that ensures air tightness and waterproof performance at the power supply cord insertion location in the back cover for a lamp body of a vehicle lamp, and reduces the man hours required for fixing the power supply cord to the back cover.
Means described hereunder are adopted in order to achieve the above-mentioned goals.
In the back cover for a lamp body, an outer wall protrudes from a back face of the back cover so as to surround the cord insertion hole for inserting the power supply cord that supplies current to the light source bulb. A resin mold region for pouring and then curing a soft synthetic resin (hot melt resin) is formed inside of a space surrounded by the outer wall. The configuration replaces a bushing member, which was used in inserting and fixing the power supply cord to the back cover. Accordingly, the steps of inserting the power supply cord with respect to the bushing, or installing and fixing the bushing can be eliminated. As a result, the number of man hours required to install the power supply cords can be reduced while air tightness and waterproof performance can be ensured with a simple method of plugging the cord insertion hole portion with synthetic resin. The soft synthetic resin (hot melt resin) may suitably be, for example, polyamide hot melt resin, denatured olefin hot melt resin, and the like.
In another implementation of the back cover for a lamp body, a protruding inner wall is provided in a location away from the outer wall. The inner wall is located in the resin mold region formed by the outer wall surrounding the cord insertion hole formed in the back cover. The inner wall provided inside the resin mold region blocks the inward flow of the soft synthetic resin that is generated during cooling and fixing of the soft synthetic resin. Accordingly, shrinkage of the synthetic resin during cooling and fixing is controlled, so that a gap does not easily form between the cured synthetic resin and the outer wall or the like.
In another implementation of the back cover for a lamp body, the height of the inner wall provided in the resin mold region is shorter than that of the outer wall. In particular, if the height of the inner wall protruding from the back face of the back cover is denoted by h and the height of the outer wall is denoted by H, then h less than H. Consequently, soft synthetic resin can be filled throughout the mold region surrounded by the outer wall even if the filling work is conducted from a single location. Moreover, by limiting the height h of the inner wall to within a predetermined range, portions not filled with the soft synthetic resin (such as gaps) inside the inner wall do not form easily. Also, even if a gap were to form in this inside region, air tightness and waterproof performance are not impacted.
As described above, the back cover for a lamp body according to the present invention simplifies the step for inserting and fixing the power supply cord to the back cover. Thus, assembly of the vehicle lamp achieves improved workability. Further, the structure contributes technically to the improvement of the quality of vehicle lamps through ensuring air tightness and waterproof performance of the lamp housing.